In many types of printing, particularly flexographic printing, offset printing and screen printing, there is an advantage in using seamless sleeves as printing elements instead of plates wrapped around printing cylinders. Seamless sleeves allow printing of continuous patterns. The use of seamless sleeves allows printing presses to operate in a smoother manner. Before a sleeve can be mounted on a printing press it has to be imaged and processed, although some materials are available today which do not require processing. Prior art laser imaging devices for imaging such sleeves were built in the general form of a lathe. Such machines have: a mandrel on which a sleeve can be mounted, a fixed headstock for driving the sleeve, a moveable tailstock for supporting the sleeve, and a travelling laser imaging head. In these systems the travelling tailstock moves on tracks in order to accommodate sleeves of different lengths. Replacing a sleeve involves moving the tailstock away from the headstock, removing the mandrel from the exposure machine and removing the sleeve from the mandrel. Typically the sleeve is removed from the mandrel by connecting an air hose to the mandrel and pressurizing the inside, causing air to leak out from small holes under the sleeve. Such an air flow expands the sleeve and creates an air bearing, allowing the sleeve to slide off the mandrel and be replaced by a blank sleeve.
It is desired to simplify this multi-step process. There is a need for a simpler process that is more automated. Prior art more automated sleeve loading existed only on flexographic presses, however it was limited to a fixed size sleeve (unless press was re-configured for a different print format) and did not include some of the automatic steps of the present invention. In an exposure machine for sleeves it is desired to handle a large range of sleeve diameters and lengths without a large set-up process between sizes. The reason for that is that a single exposure machine typically has to serve a large number of presses, each of a different format. For this reason presses did not require easy changing of mandrels, just sleeves. It is also desired to allow the exposure machine to be built from a simple fixed length frame instead of an adjustable length. The present invention solves these problems and further improves the procedure of loading and unloading sleeves from an exposure device.